Use the new `_Default_Foo` typealias trickery to define a conditional
default type witness for the collection `Indices` associated type, so
`Indices` becomes `CountableRange<Index>` when the `Index` type is
`Strideable` with `Int` as its `Stride` type.
This fixes the major regression with associated type inference for
“minimal” random access collection types with `Int` index types, which
has come up in a number of places.
Note that I dropped the `@_implements` requirement because `_Default_Foo`
is already off in its own namespace, and eventually we should get a real
syntax for this.
Fixes rdar://problem/35035322.
- Create the value witness table as a separate global object instead
of concatenating it to the metadata pattern.
- Always pass the metadata to the runtime and let the runtime handle
instantiating or modifying the value witness table.
- Pass the right layout algorithm version to the runtime; currently
this is always "Swift 5".
- Create a runtime function to instantiate single-case enums.
Among other things, this makes the copying of the VWT, and any
modifications of it, explicit and in the runtime, which is more
future-proof.
* Nest various top-level Iterator and Index types, and flatten extensions.
* Fix tests from nesting iterator
* Nest Unsafe*BufferPointer.Iterator, extensionify UnsafeBufferPointer
* Degyb LazyCollection
* Nest Flatten iterator and index
* Eradicate IndexDistance associated type, replacing with Int everywhere
* Consistently use Int for ExistentialCollection’s IndexDistance type.
* Fix test for IndexDistance removal
* Remove a handful of no-longer-needed explicit types
* Add compatibility shims for non-Int index distances
* Test compatibility shim
* Move IndexDistance typealias into the Collection protocol
* Refactor Indices and Slice to use conditional conformance
* Replace ReversedRandomAccessCollection with a conditional extension
* Refactor some types into struct+extensions
* Revise Slice documentation
* Fix test cases for adoption of conditional conformances.
* [RangeReplaceableCollection] Eliminate unnecessary slicing subscript operator.
* Add -enable-experimental-conditional-conformances to test.
* Gruesome workaround for crasher in MutableSlice tests
After changes to stdlib and type-checker related to removing
of the `_Strideable` it's now possible to properly support
iterator types for *ClosedRange without any workarounds.
Resolves: rdar://problem/25584401
Using && here causes us to go down a SILGen path that guarantees that self will
be evaluated over the entire && expression instead of just the LHS. This cause
the uniqueness check to always return false at -Onone. At -O, the optimizer is
smart enough to remove this issue.
rdar://33358110
For Swift 3 / 4:
Deprecate the spelling "ImplicitlyUnwrappedOptional", emitting a warning
and suggesting "!" in places where they are allowed according to
SE-0054.
In places where SE-0054 disallowed IUOs but we continued to accept them
in previous compilers, emit a warning suggesting "Optional" or "?" as
an alternative depending on context and treat the IUO as an Optional,
noting this in the diagnostic.
For Swift 5:
Treat "ImplicitlyUnwrappedOptional" as an error, suggesting
"!" in places where they are allowed by SE-0054.
In places where SE-0054 disallowed IUOs, emit an error suggestion
"Optional" or "?" as an alternative depending on context.
